Subject:
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RE: IR tower question
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Newsgroups:
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lugnet.robotics
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Date:
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Thu, 18 Nov 1999 08:10:40 GMT
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Original-From:
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Niinikoski Juha <JUHA.NIINIKOSKI@MIKROLOG.FInomorespam>
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Viewed:
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601 times
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I stripped my IR tower few days ago and draw a partial schematics out of it.
TX side.
There are two IR diodes connected series. Low power level feed is 100 ohm
and high level is 5.6 ohms. Low range diode current is somewhere around 50
mA. I have not measured high range but 5.6R should give 1A peak current.
There is only a small storage capacitor for storing required TX energy.
38 kHz carrier bursts are generated with 74HC132 smith trigger gate
oscillator (not very accurate). There is a frequency adjustment pot for
tuning the oscillator. Burst gating is done with same quad nand gate chip.
RX side
Main component is Telefunken TSOP1138 IR receiver chip. It does burst
filtering and decoding. RS232 level translation is done with a couple of
transistors. This Telefunken chip seems to be more tolerable for carrier
frequency and carrier duty cycle errors than others. I have tested my own IR
things with Sharp ISU60 and Rohm RPM6938 and found their 38 kHz carrier
quality requirements higher.
Link idle state is nothing. Start bit is 38 kHz burst and so on.
Rest of the stuff inside IR tower is battery saving logic which is
irrelevant here.
Juha
Lego related PIC projects
> -----Original Message-----
> From: Robert Eddings [SMTP:webmake@bellsouth.net]
> Sent: 18. marraskuuta 1999 6:06
> To: lego-robotics@crynwr.com
> Subject: IR tower question
>
> This is in reference to a problem I am having programming the internal
> IR of the Palm device but the information I need is about the LEGO IR
> tower so I am posting it here.
>
> It is my understanding that the LEGO IR tower does a direct conversion
> of serial data to IR pulses. I mean, sense the IR tower uses a null
> modem cable to connect to the serial port, I thought that the tower
> simply converted the high and low voltage to on and off IR pulses
> respectively. Is this correct? Is it adding signal information? Does it
> invert bit polarity (0 bit = on)?
>
> Any insights or speculation would be helpful.
> Robert Eddings
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